Caster cups



CASTER CUPS Betty Auer, Chicago, Ill.

@riginal application December 29, 1949, denial No. 135,815, novt7 PatentNo. 2,699,628, dated January 18, 1955. Divided and this applicationNovember 12, 1954, Serial No. 468,197

2 Claims. (Cl. L15-137) This invention is concerned with caster cups andmay be considered a division of my copending application Serial No.135,815, led December 29, 1949 (now Patent No. 2,699,628, dated January18, 1955) as a continuation-in-part of prior application Serial No.118,634, filed September 29, 1949, which has become abandoned.

The invention furnishes improved supports of the caster cup type, formusical instruments and other equipment or furniture, which provideamong others the following advantages, namely, first, a relatively largecontact area with the supporting surface, iioor or floor covering,thereby protecting the material of the supporting surface againstdamage; second, fixing the supported piece of equipment againstdisplacement; third, elevating the supported piece of equipment by avery small, practically negligible amount, thus, for example, preventinginterference with vacuum cleaning of the supporting surface or itscovering and, in the case of upright pianos or spinets which are usuallystanding against a Wall and need caster supports only underneath thefront legs, preventing visible rearward tilting of the instrument;fourth, counteracting angular forces set up, for example, in playing apiano, to prevent creeping of the instrument and consequent bulging ofthe floor covering such as a rug orcarpet underneath the caster support;fifth, damping the transmission of Vibrations fromthe supported piece ofequipment, for example, a musical instrument, to the supporting surface,thereby contributing to improvement of the tone quality thereof; andsixth, furnishing supports which have decorative functions in additionto their utilitarian aspects.

The `foregoing and other objects and features of the invention willappear from the description of the embodiments which is rendered belowwith reference to the accompanying diagrammatic drawings, wherein Figs.1-8 `show various embodiments of the invention each in diagrammaticcross-sectional view;

Fig, 9 illustrates a further embodiment in diagrammatic elevational sideview; and l Fig. 10 is a diagram to aid in explaining the operation ofthe invention.

It is assumed that each structure shown in the drawings is eithercircular and has a diameter of approximately 4 inches, or that it isapproximately 4 inches square.

Referring now to the drawings: The device shown in Fig. 1 comprises arelatively thin top plate 11 made of suitable relatively rigid material,for example, stainless steel or aluminum, and forming a centraldepression 12` for receiving the load-bearingelement such `as a casterwheel or caster button of a piece of furniture, piano or otherequipment, and for holding the loadbearing element against lateraldisplacement. Suitably secured, that is, molded or molecularly bonded tothis plate 11 and forming a unitary structure therewith, is a bottomlayer 13 of a relatively elastieor resilient material such as rubber ora rubberlike composition. The peripheral portion of the top plate may beturned slightly downwardly States Patent to embrace a portion of thelayer 13 peripherally thereof.

The exposed top surface of the plate 11, as well as the exposed surfaces`of corresponding elements in some of the remaining embodiments, may befinished as desired, polished or buffed, or anodized in desired colorsfor any intended decorative effect, for example, any in tendedrug-matching or color contrasting eifect.

The structure shown in Fig. 1 as well as each of the structures shown inthe remaining figures, assumed to be circular or square, may of courseassume other shapes, for example, rectangular, elliptic, oblong or anyother desired and suitable shape, and the corresponding centraldepressions shown in the various embodiments, such as the depression 12shown in Fig. l, may likewise be made to assume any desired and suitableoutline.

The top plate 11 may be less than 1/6" thick, and the amount ofexpensive metal is thus kept at a minimum. The structure is neat inappearance, relatively thin, its thickness being less than 1A throughoutany portion thereof. The device is also easy to manufacture and fulfillsthe previously indicated functions, whether it is used on a licorcovering or directly in contact with a iioor.

The embodiment illustrated in Fig. 2 is assumed to be circular in shape.It comprises a generally domeshaped or inverted dish-shaped relativelythin metallic plate 14 forming the central depression 15. The undersidemay be filled with a layer 16 of rubber or rubberlike material havingthe characteristics mentioned before. The load will be effectivelydistributed, due to the dome shape of the plate 14. The structure willyield the intended advantages just like the embodiment shown in Fig. 1.lts thickness at any point may be less than 3%".

if the structure shown in FiggZ is to be made rectangular or the likeinstead of circular, this may be done by forming, for example, four flatsides which converge upwardly to produce a flat pyramid'. The termdomeshaped is intended to cover a circular structure such as shown inFig. 2, as well as a structure made in the form of such flat pyramid orthe like.

Fig. 3 illustrates a modification which'furnishes the functions andfeatures of Fig. `2, while requiring less'material for the resilientbottom padding. `The top plate forms, in this case,-an elevatedportionf17 which surrounds the central depression 18 and a flangelikeperipheral portion 19. Underneath the top plate is again the resilientbottom layer or padding, as indicated in Fig. 3 by numeral Ztl.Reinforcing ribs 21 may be provided, if desired, to assist in carryingand downwardly distributing the load. These ribs in a circular structuremay extend from the elevated portion 17 radially outwardly to the edgeof the top plate, and in an angular structure they may extend from theelevated inner portion 17 outwardly to the corners of the top plate. Thecorners of the device may be suitably rounded to present a neat andsmooth appearance.

` rlhe structure shown in Fig. 4 comprises a base plate 22 suitablyshaped, as already explained, which is made of synthetic material, suchas Lucite, nylon, Plexiglas or the like. These materials may be made ofopaque or translucent, and in practically any color, to achieve desireddecorative effects. They may be easily V machined or molded in anydesired shape.`

The base plate 22 of Fig. 4 is provided with a recess in which isdisposed the top plate 2,3 made of suitable rigid material, for example,metal such `as stainlesssteel or aluminum, and forming again a centraldepression 24 for receiving and holding the `loadbearing element. VThetop plate 23 may be removable from the base plate 22 and shims, asindicated iat 2S, may be usedto adjust` its position in and on the topplate. This may be desired,

' plate 26, which is made in the form of an an' ansiosa for example, inconnection with musical instruments, for

' putting them in level position on slightly sloping floors.

The load on the rigid member 23 is evenly distributed downwardly to thebase plate 22, which by its inherent rigidity transmitsthe load in turnto the supporting surface underneath and over substantially its entirebottom area, justas in the case of the structures already distively thinringlike member in the central aperture of which is disposed the shank27 of the gcncluily mushroom-shaped top plate 28 forming the annularfiar .Y 29 and the central depression 30. The annular ba: ber 26 formswith the shank 27 a bottom surface 'which is suitably bonded theresilient bottom layer 3l. The top plate 28 may be removable from theremainder of the structure or xedly attached, as desired.

ber 32 which corresponds essentially to the base in i 2-2 of Fig. 4,having a recess in which is disposed a resilient ringlike insert 33 madeof rubber or the like, forming in turn a central aperture whichaccommodates the shank 34 of the generally mushroom-shaped top platemember 35, the latter forming the peripheral flange 3o and the centraldepression 37. The bottom of the stem of the mushroom-shaped top plateforms a cavity with the base member 32 to enhance the damping feature ofthe device. This particularrstructure may be used with good effect ondoor coverings as well as in direct contact with a licor. The top platemay again be either removable or may bc in xed position with respect tothe other elements of the device.

The embodiments made in accordance with Figs. 7 and 8 are particularlysuitable for molding processes, Fig. 7, if used for supporting avibrating structure such as a piano, being adapted to give best resultsin contact with a door covering, and the device made in accordance withFig. 8 being adapted for effectively supporting such vibrating structurein contact with either a door or a oor covering. It will be appreciatedof course that a oor covering, rug or the like will function as a mediumfor damping vibrations if it is contacted over a relatively large areaby devices of the present invention.

Referring now to Fig. 7: The device comprises a base plate 38, made ofmoldable material, for example, rubber or the like, or of material ofthe class of materials including Lucite, nylon, Plexiglas r the like.Molded into and molecularly bonded to the body of the plate 38 is theangular flangelike extension 39 of the thin metallic top plate whichforms an elevated portion 40 surrounding a central depression 41.

The device made in accordance with Fig. 8 is similar to the one shown inFig. 7, and in a sense also similar to the structure shown in Fig. 5,comprising, as it does, an annular base plate 42 which may again be madeof material of the class of Lucite, Plexiglas or nylon. Theload-receiving top plate having the central depression 43 forms a flange44 which terminates in an angular portion 45. The latter is embedded inand molecularly bonded to the body of the ringlike annular base member42. The top surface of the flange 44 is substantially liush with the topsurface of the base plate member 42, and the bottom of the top plateforming the depression 43 is substantially ush with its bottom surface.On its underside, the structure is provided with a resilient padding,for example, a

' suitable rubber padding 46, as already discussed in conmay beprovided, if desired.

Y new device.

While the load-receiving top plates in the various em bodiments, andparticularly those in Figs. 4-6, are shown as being made of metal, thisis not absolutely necessary. it is necessary, however, that these topplates be made of relatively rigid and sturdy material which by itsrigidity tends to distribute the load downwardly over a large area ofthe underlying structure, so that the underiying structure, andparticularly the bottom member thereof, may be operatively effectivesubstantially throughout its entire contact area with the supportingsurface extending underneath, and that they be made of material which isnot easily marred by the load-bearing element.

The structures shown in Figs. 4, 5 ando may be prod ced by machining,without requiring any unching, form' ig or molding operation as is thecase in Figs. l-3 a d gs. 7 and 8, respectively.

'l ie virtue of using synthetic material as indicated in connection withthe embodiments shown in Figs. 4-8, is that these materials havesur'licient inherent rigidity to prevent warping when used forsupporting loads as dcscribed herein and as indicated in the drawings,thus substantially uniformly utilizing substantially the entire bottomarea for load-transmitting purposes to the supporting surfaceunderneath, and yet these materials have a certain degree of resiliencywhich is beneficial particularly when the corresponding device is usedas a support under the leg of a vibrating body, for example, a musicalinstrument. These materials therefore aid in absorbing or damping thevibrations, beneiitting the tone quality of the correspondinginstrument. The phenomenon of coid flow is substantially avoided by thelarge Contact area provided between the base plate and its associatedtop plate. Caster cups made according to the invention have been testedby a commercial testing laboratory and have been found to support loadsup to 11,000 pounds without showing any visible distortion'.

The structure shown in Fig. 9 has the virtue of low cost in production.It comprises a relatively thin base plate 4S which may be made ofmetall, with ears 49 punched out from it to hold in position the pad 5l)which may be made of relatively resilient material, and forms thecentral depression 51 for receiving and centering the load-bearingelement. The pad 51 may be provided with a metallic top plate forreceiving the load-bearing element.

All fthe embodiments disclosed have certain features in common. Forexample, each structure furnishes, first, a generally platelike,generally at device the thickness of which does not exceed approximatelyS; throughout any portion thereof. In the case of the embodiments shownin Figs. l, 7 and 8, this dimension is lless than 1A. The advantageresulting from these dimensions resides in economy in the use ofmaterials. Second, the deepest point of the central depression in eachdevice is spaced from the plane of its bottom contact surface by 3fm orless. Specifically, in the structures made in accordance with Figs. 1 3,5, 7 and 8, the distance is approximately 1/8 or less; and in thestructures shown in Figs. 4 and 6 the distance is approximately 3A6 orless; while the distance in the structure shown in Fig. 9 is just atriile more than 1/8. These dimensions furnish the important advantageof placing the supporting point for the load-bearing element very closeto the supporting surface, thereby giving further advantages which willlbe realized from the following discussion with reference to Fig. 10.

The prominently drawn horizontal line in Fig. l0 desig nates the bottomplane of the contact surface of the The prominently drawn curved line Adesignates the central top depression, the deepest point of which isassumed to be spaced from the bottom plane by approximately LV16. Thecurved line B designates a central depression, the :deepest point ofwhich is assumed to be lspaced from the bottom plane by about 1A.

The dimensions l11-l1/22 and 2.1/2", at the bottom of the diagramindicate the radii of four devices, assumed, for the sake of example, tobe circular in shape,

" and thus having their respective outer edges at`` points W-X-Y and Z,respectively. We thus have four devices with diameters of 2.5--3-4" and5", respectively. These devices may be generality square instead ofcircular, and the bottom dimensions will thus refer to the distance fromthe center to the nearest outer edges thereof, giving us Idevices whichare `2.5---3--4--5 inches square, respectively. i The resultingoperatively effective` contact areas (with supporting surfaces) areindicated at the right of Fig.` l0. The areas indicated are approximate,frac#V tions `having been neglected, and the rounding of the corners inthe case of square structures having also `been neglected.

The diagram shows 'that the smallest embodiments of 2.5 `diameter or 2.5square will give us operatively effective contact areas of about 5 and 6square inches, respectively. This feature is therefore common to allembodiments. The largest assumed embodiments of 5" diameter or 5" squarewill result in operatively effective contact areas of and 25 squareinches, respectively.

The smallest embodiment W, of 2.5 diameteror 2.5 square has beenincluded mainly for the purpose of comparison. lt willI probably berarely used in practice, and we may therefore assume that the smallestcontact areas which will result in most instances of use will be on theorder of approximately 7 to 9 square inches. The largest size Z, of 5"Idiameter or 5 square, as indicated in Fig. l0, will probably satisfyany ordinary requirements for large devices of this type for home use.

The lines drawn from the outer edge of any one of the embodimentsthrough the deepest point of the depression A will result in the anglesindicated at the left of Fig. 10. The smallest device W of 2.5" diameteror 2.5" square, will thus produce an angle of less than 9, while thelargest device Z will producean angle of less than 5. In most of thedevices, for example, Figs. 1,2, 3, 5, 7, 8 and 9, the angle will beappreciably smaller than indicated, because the distance between thedeepest point of the depression is appreciably smaller than 9%16 and, ifwe assume the :distance to be about a (Figs. l, 2, 3, 5, 7, 8 and 9),the angles produced by the four assumed structures will be about 7-54vand 3 respectively.

lt should be observed, for comparison, that a device W, of 2.5 diameteror 2.5 square, with the deepest point of the depression B spaced fromthe plane of the bottom surface by 1A, would produce an angle of morethan 12. The corresponding angle produced by the largest embodimentwould be in the neighborhood of about 9.

Another common feature resides in the dimensional relationship betweenthe vertical distance from` the central point of the depression B to theplane of the bottom contact surface and the lateral distance from avertical line drawn through the central point of the depression to theouter edge of ithe device. If we assume this vertical distance to beabout 1/s, in any of the embodiments W-X-Y-Z (see also Figs. l and 4-9)the noted lateral distance will be, respectively, 10-12-16 and 20 timesgreater than the vertical distance; and, if the latter is assumed to beon the order of about as shown in Figs. 2 and 3, the lateral 'distancewill be in the four respective embodiments, in round figures, 6-8-10 and13 times greater than Ithe vertical distance. The lateral distancetherefore is in any case always in excess of about 6 times the verticaldistance, and will be in most cases about 8 times greater, because itmay be assumed that embodiments of the size X and larger will be morefrequently used than -th'e smal-l size indicated in Fig. l0 at W.

The space marked C in Fig. l() indicates the distance from a peripheralpoint of the central depression A or B to an outer edge of the device W,which will be about Ss, or about 5 times the depth of the centraldepression, if such depth is assumed to be about 1/5", as shown in Figs.l and 4 9, and over 3 times the depth, if it is on the order of aboutim", as shown in Figs. 2 and 3. The corresponding gures for thesuccessively larger embodiments X`Y and Z, each with a centraldepression about Ms deep, will be about 7-11 and 15 times the depth;and, if we assume the depth to be about W16, they will be about 4-7 andl0 times such depth. Another feature also common to all embodimentstherefore is that the distance from a peripheral point of the centraldepression to an outer edge of the base member is on the order of about3 times the depth of the central depression, or more. ln most practicalinstances this distance will be on the order of about 4 times the depthof the depression, or more, as in the case of the embodiment X andlarger embodiments, because the smallest size W will probably berelatively rarely used, as mentioned before. The `figures and dimensionsgiven will also apply.in embodimentsV of oblong, elliptic, rectangular,etc., shape where the nearest edge of thebase member is atfthe pointsW-X-`-YZ, respectively, and such embodiments will of course give stillmore favorable conditions. The dimensional features which are commontothe various embodiments may now be briey summarized.

The thickness of the new device, in any of its embodiments, at any pointthroughout its body is less than and the distance from a central pointof the depression to the plane` of the bottom surface is always about1A" or less and, as shown, actuallyabout W16" or less.` The operativelyeective contact area is always in excess of about 5 square inches and inmost cases, assuming the smallest practical embodiment to be 3" indiameter or 3 square, or of a different but similarly dimensioned shape,it will be about 7 square inches or more. i The angle formed by a linedrawn from the nearest edge of The device through a central point of thedepression with the plane of the bottom surface will always be less than12 and about 9 or less, and in most practical embodiments it will beabout 7 or less. The distance from a peripheral point of the centraldepression to an outer edge ofthe device will always be at least 3 timesthe depth of the depression, and in most practical instances it will beon the order of at least about 4 to 7 times such depth, because it canbe assumed that embodiments X and larger, with depressions about r1/s to/e deep, will predominate in practical use. Finally, the lateraldistance measured from a vertical line drawn through the central pointof the depression to an outer edge of the device will always be at leastabout 6 times the vertical distance from such centralpoint to the planeof the bottom surface.

In the case of the specific embodiments shown in Figs. l, 7 and 8, thethickness of the device at any 4'point throughout its entire extent willbe about 1A or less. In the case of the species shown in Figs. l, 2, 3,5, 7, 8 and 9, the distance from a central point of the depression tothe plane of thebottom surface will be about 1A" or less, and the angleformed with the plans of the bottom surface by a line drawn from theedge of the device through the central point of the depression willalways be less than 7 and in most practical instances about 5 or less.

The various dimensions and their interaction in the practical use of theinvention are believed to contribute to the economy of production of thenew devices and to the favorable and efficient operation thereof. Aminimum of material is used exactly where needed to give the intendedoperation. The piece of equipment to be supported is elevated from theunderlying supporting surface by only a very small, and in mostinstances practically negligible amount. The very small angles formedalong lines drawn through the central points of the central depressionsof the devices with the planes of the bottom surfaces thereof counteractand favor the damping of vibrating forces, thus contributing, in thecase of musical instruments, to the improvement of the tone quality; andthey also assist in efficiently counteracting and absorbing angularforces which attempt to displace the corresponding piece of equipmentrelative to the supporting surface, thus avoiding its creeping andtherewith subavenues stantially eliminating thecreeping and buckling offloor .coverings.

Y device which elevates a piece of equipment by an appreciable amountfrom its supporting surface. The angle drawn from the outer edge of sucha device through the point where the caster. or caster wheel reststhereon will then be correspondingly large, and the larger it is thesmaller will ybe the damping effect and the lgreater will be thetendency of the device to tip on its edge in response to angularV forcesexerted thereon by the piece of equipment, thus preventing efficientuseof the potential contact area of the device with the supportingsurface. In the case of the invention, such angular forces arecontrolled, and substantially the entire potential bottom area of thedevice is always operatively effective to support the load.

Modifications above and beyond those discussed in the foregoingexplanations are possible. For example, the device of Fig. 7 may bemodified -by forming the loadreceiving top plate, as shown in Fig. 7a.The material of the top plate is bent upon itself at 40a t-o form alaterally inwardly directed recess S1 from which extends the skirtportion 39a forming the peripheral bead also shown in Eig. 7. Thematerial of the lbase plate 38a wi-ll ilo-w into the recess 51, duringthe molding process, locking the peripheral top portion yof the baseplate to the load-receiving top plate. The `structure shown in Fig. 8may be similarly modified.

Rubber or rubberlike material may take the place of the syntheticmaterial shown in Figs. 7-8. The structure shown in Fig. 7a will serveparticularly well with rubber, because the peripheral top portion willbe locked against peeling in the recess 51, and downwardly as well aslaterally outwardly effective pressure will be transmitted to theperipheral portion lof the rubber plate by the bead Y carried by theskirt 39a, thus preventing dam-age to the rubber.

Means may be provided lfor removably fastening the supporting device, inany of the embodiments shown, to the load-bearing element, particularlyin cases where the loadbearing element is in the form of a casterbutton, for example, at the free end of the leg of a piece of furniture.Such means may take the form of a small locking pin having yslightlyenlarged ends for insertion into holes formed in the caster button andin the top plate of the corresponding supporting device, respectively.It is also possible to make either the top plate of the supportingdevice or part thereof, or preferably the caster button, in the form ofa permanent magnet which will hold the device removably Ain positionunder the load-bearing elet ment.

Such means willy -be useful especially in connection,` with pieces offurniture, for example, chairs or the like, which are frequently movedabout.

The term `,floor covering includes, of course, carpets 'and rugs, aswell as cork -or linoleum coverings or the like.

It will be seen from the explanations given .above that changes may bemade within the scope and spirit of the `appended claims.

I claim:

-l1 ,Afdevice yfor supporting a load-bearing element in the manner of acaster Icup comprising a generally platelike generally flat base membermade of moldable plastic material with its opposite sides extendingsubstantially in parallel planes, la disklike metallic member having acentral depression formed therein and having a ilange extending`radially, outwardly from said depression, said flange having a firstportion which Vis elevated relative to the plane of the `deepest pointof said depression and a second portion which, is disposed in a planesubstantially coinciding with the plane of said deepest point, at leastsaid second portion of said-flange being embedded and molecularly bondedin the material of said base member along an area between the oppositesides thereof `securing sai-d disklike metallic member substantiallypermanently and relatively fixed with respect to said base member, saidcentral depression formed in said disklike metallic member being adaptedto receive a load-bearing element in load-transfer engagement therewith.

2. The structureY delinedin claim 1, wherein the outer surface of saidfirst portion of said .flange of said disklike metallic member which isradially adjacent said central depression is llush with the surface ofthe correspon-ding side of said base member.

, References Cited in the le of this patent UNITED STATES PATENTS

